Simplified closure mechanisms have been proposed using bonds (plastic welds) to create restricted passages which tend to close upon the gelation of polymer and the inversion of the bag. Publication U.S. 20040064112 is such as bag. However in the applications' configuration, with two openings and four bond lines, the flow of liquid into the bag is so restricted that its use, for example, as a urine collection bag is impractical because the portion of the bag above the bonds has inadequate capacity for liquid quantities on the order of twenty ounces, and during the extended time it would take for whatever quantity of liquid that can be accommodated in the upper portion of the bag will spill out if the bag is shaken or inverted.
Liquid collection bags have been developed for various purposes to admit liquid into a reservoir and then use an absorbent such as polymer to gel the liquid and prevent it from leaking out of the bag.
For example, liquid collection bags have been used to collect urine and which feature a funnel insert in a flexible plastic bag and with a one-way valve. As in the U.S. Pat. No. 5,116,139 the funnel itself can also serve as a one-way valve as the polymer expands. This configuration is generally satisfactory in function but requires an extra manufacturing step of first attaching an inverted funnel outside of the bag to the top of the bag and second pressing the funnel inside out so that it is contained within the bag.